Hitherto, various perpendicular magnetic recording systems for magnetizing a magnetic layer formed in a magnetic recording medium in the thickness direction of the layer have been investigated for increasing the recording density of magnetic recording media. A magnetic head used for the recording system is generally composed of a principal magnetic pole facing a magnetic layer of a magnetic recording medium, an auxiliary magnetic pole paired with the principal magnetic pole, and a coil coiled around the auxiliary magnetic pole or the principal magnetic pole.
In such a magnetic head, the reproducing power and the resolving power can be easily increased since the foregoing principal magnetic pole can be reduced as thin as possible. However, when the principal magnetic pole becomes thinner, there occur problems of the magnetic saturation of the principal magnetic pole and the reduction in output at reproduction. For preventing the occurence of such problems, a high saturation magnetic density flux and an excellent soft magnetic character are required. However, by the use of permalloy which has hitherto been used as the principal magnetic pole, it is difficult to sufficiently increase the permeability and the saturation magnetic density. Accordingly, there is a limit in reproducing and resolving power in such a magnetic head.
Also, a thin layer type magnetic recording head is composed of a 1st core thin layer, a non-magnetic thin layer, and a 2nd core thin layer formed in laminate layers on a base plate composed of a non-magnetic material by sputtering or vapor deposition, and the thin layer type magnetic recording heat constitutes a thin layer magnetic head, together with a thin layer magnetic reproducing head as a pair. Such a thin layer magnetic head is used for, for example, a memory of a computer and, in this case, for increasing the recording efficiency in the thin layer magnetic recording head, it is necessary to use a soft magnetic material having a high permeability and a high saturation magnetic flux density as the 1st and 2nd core thin layers.
However, in the case of using permalloy, etc., which are conventionally used for the core thin layers, the core thin layers cause magnetic saturation at recording since permalloy, etc., has a low saturation magnetic flux density and a low permeability and hence in the case of recording signals in a magnetic recording medium having a high saturation magnetic flux density, such as a metal tape or a chromium dioxide tape, the recording efficiency is inferior.
Thus, for increasing the recording efficiency, it may be considered to prevent the reduction in recording efficiency by increasing the turn number of coils or increasing the recording electric current. However, it is difficult in the structure of the thin layer magnetic head to increase the turn number of coils or the turn number is restricted to about 3 turns, whereby a sufficient effect is not obtained. On the other hand, the increase of the recording electric current is accompanied by an increase in the amount of generated heat, the occurence of breaking, and the occurence of the deterioration of magnetic properties of the core thin layers.
Also, a thin layer magnetic reproducing head is composed of a base plate composed of a non-magnetic material, a 1st magnetic shield thin layer formed on a base plate, a magnetic resistance effect element (hereinafter, is referred to as MR element) formed on the 1st magnetic shield thin layer, a 2nd magnetic shield thin layer, etc., formed on the MR element. The thin layer magnetic reproducing head constitutes a thin layer magnetic head together with a thin layer magnetic recording head in a pair and such a thin layer magnetic head is used, for example, for a memory of a computer.
The magnetic shield thin layer used for the thin layer magnetic reproducing head is required to have a high permeability and a high saturation magnetic flux density for sufficiently exhibiting the function of the shield. As the magnetic shield thin layer, a binary permalloy composed of an iron-nickel alloy or a ternary permalloy composed of the iron-nickel alloy and a third element such as chromium, molybdenum, copper, etc., is usually used. However, in permalloy, it is generally difficult to sufficiently increase the permeability and saturation magnetic flux density and hence a sufficient shield effect cannot be obtained.